Carburetor start pump circuit

Abstract

A carburetor start pump circuit, for starting an engine has an auxiliary fuel pump mounted on a relatively standard carburetor body, a start pulse passage extending through the carburetor body to the auxiliary fuel pump, and a fuel circuit having an intake side which extends from a metering chamber of the carburetor body to the auxiliary fuel pump and a discharge side which is interconnected to the intake side and extends from the auxiliary fuel pump to a throttle bore in the air intake of the carburetor body. To prevent the engine from stalling, a restriction jet is placed within the start pulse passage to prevent the auxiliary fuel pump from discharging fuel into the throttling bore when the engine transmits pulses at high frequencies.

1. A carburetor, comprising:
 a body; 
 a fuel pump mounted on the body; 
 a first pulse passageway extending through the body to the fuel pump, and 
 a restriction within the pulse passageway, wherein the restriction is calibrated such that it prevents the fuel pump from operating without user intervention when engine pulses are above a predetermined frequency and allows the fuel to operate when engine pulses are below a predetermined frequency. 
 
   
   
     2. The carburetor in  claim 1 , wherein the restriction is calibrated such that the restriction substantially chokes off high frequency pulses. 
   
   
     3. The carburetor in  claim 1 , wherein the restriction chokes off high frequency pulses sufficient to prevent the fuel pump from operating, and further wherein the restriction passes through low frequency pulses sufficient to operate the fuel pump. 
   
   
     4. The carburetor in  claim 1 , wherein the restriction is a jet. 
   
   
     5. The carburetor in  claim 1 , wherein the restriction is in a beginning of the pulse passageway. 
   
   
     6. The carburetor in  claim 1 , wherein the restriction is in an end of the pulse passageway. 
   
   
     7. The carburetor of  claim 1 , further comprising
 a first fuel passageway interconnecting the fuel pump to a metering chamber in the body; and 
 a second fuel passageway interconnecting the fuel pump to a throttle bore in the body. 
 
   
   
     8. The carburetor of  claim 7 , further comprising an inlet check valve interposing the fuel passageway and a pumping chamber in the fuel pump. 
   
   
     9. The carburetor of  claim 7 , further comprising an outlet check valve interposing the fuel passageway and a pumping chamber in the fuel pump. 
   
   
     10. The carburetor of  claim 9 , wherein the outlet check valve is spring loaded. 
   
   
     11. The carburetor of  claim 1 , further comprising a metering jet. 
   
   
     12. The carburetor of  claim 1 , wherein the fuel pump includes a diaphragm. 
   
   
     13. The carburetor of  claim 1  wherein the pulse passageway has an open mode during engine start-up and a closed mode during all other modes of engine operation. 
   
   
     14. The carburetor of  claim 1  further comprising a primer bulb interconnected to the fuel pump. 
   
   
     15. A carburetor comprising
 a body; 
 a fuel pump mounted on the body and driven by a pulse from an engine's crankcase during start-up of an engine; 
 a pulse passageway extending through the body to the fuel pump; 
 first and second fuel passageways connected to the fuel pump; and 
 a restriction jet within the pulse passageway, wherein the restriction jet is adapted to prevent operation of the fuel pump when the pulse from the engine's crankcase is above a predetermined frequency without user intervention. 
 
   
   
     16. The carburetor of  claim 15  wherein the first fuel passageway operably interconnecting the fuel pump to a metering chamber in the body, and the second fuel passageway operably interconnecting the fuel pump to a throttle bore in the body. 
   
   
     17. The carburetor in  claim 15 , wherein the restriction jet is positioned and calibrated such that the restriction jet substantially limits the pulse from the engine's crankcase to the fuel pump at high frequencies. 
   
   
     18. A carburetor comprising:
 a body; 
 a fuel pump mounted on the body; 
 a means for limiting the interconnection between the fuel pump and the engine's crankcase preventing the operation of the fuel pump without user intervention when the engine warms up; and 
 a pulse passageway extending through the body to the fuel pump. 
 
   
   
     19. The carburetor in  claim 18 , wherein the means for limiting the interconnection is a restriction jet within the pulse passageway. 
   
   
     20. The carburetor in  claim 18 , wherein the pulse passageway extends from the body to the fuel pump. 
   
   
     21. The carburetor in  claim 18 , wherein the pulse passageway includes a valve member mounted in the pulse passageway. 
   
   
     22. The carburetor of  claim 21  wherein the valve member is positionable to a preset engine start-up position wherein the pulse passageway is open. 
   
   
     23. The carburetor of  claim 21  wherein the valve member comprises a throttle valve shaft having a hole drilled therethrough, the hole being aligned with the pulse passageway when the throttle valve shaft is rotated to a preset engine start-up position. 
   
   
     24. The carburetor of  claim 23  further comprising
 a first fuel passageway operably interconnecting the fuel pump to a metering chamber in the body, and 
 a second fuel passageway operably interconnecting the fuel pump to a throttle bore in the body. 
 
   
   
     25. A method of enriching the air-fuel mixture in a carburetor mounted to an engine, having a crankcase, during start-up of the engine comprising the steps of:
 transmitting pulses from an engine's crankcase to a fuel pump mounted on a carburetor body; and 
 preventing operation of the fuel pump without user invention by preventing engine pulses above a predetermined frequency from reaching the fuel pump. 
 
   
   
     26. The method of  claim 25  further comprising the steps of
 drawing fuel from a metering chamber in the carburetor into a pumping chamber of the fuel pump when pulses are transmitted to the fuel pump; and 
 discharging the fuel in the pumping chamber into a throttling bore in the carburetor body when pulses are transmitted to the fuel pump. 
 
   
   
     27. The method of  claim 25  further comprising the steps of:
 rotating a throttle valve shaft in the carburetor past wide open throttle to a preset position wherein a hole drilled through the throttle valve shaft is aligned with the pulse passage way to open the pulse passageway; and 
 reverse rotating the throttle valve shaft to close the pulse passageway. 
 
   
   
     28. The method of  claim 25 , further comprising the step of
 metering the fuel into the fuel pump. 
 
   
   
     29. The method of  claim 25 , further comprising the step of
 metering the fuel out of the fuel pump.